Method of manufacturing dry cells



April 22, 1947- H. R. c. ANTHONY 2,419,244

Patented Apr. 22, 1947 2,419,244 METHOD F MANUFACTURING DRY CELLS Herman R. C. Anthony, Madison, Wis., assignor to Ray-O-Vac Company, a corporation of Wisconsin Application March 4, 1943, Serial No. 477,917

' z claims. (ci. 13s-175) This invention relates to dry cells of the type used in ilash lights and the like, and more particularly to an improved method of manufacturing the same.

'I'he primary object of the present invention is to provide an improved dry cell wherein the top closure of insulating material is secured to the top of the carbon electrode before the bobbin of depolarizing mix is inserted into the zinc can which forms the other electrode, and the bobbin is suspended from the top closure.

In the conventional dry cell it is extremely diilcult to have the carbon electrode and bobbin of depolarizing mix accurately centered in the zinc can. By the present invention the bobbin is formed with great precision with respect t0 the closure from which it is suspended and accordingly in the completed cell the parts are brought into better alignment than has heretofore been obtained.

Another object of the invention is to avoid the conventional practice of resting the bobbin on an insulating disk in the base of the cell which is required to prevent a short circuit. In the present cell it is unnecessary to provide an lnsulating disk on the bottom of the cell or to provide a guiding disk to centerthe bobbin when it is being introduced into the can. Accordingly, the bottom of the cell is as fully exposed to the action of the electrolyte as is the side wall.

The invention is particularly adapted to the manufacture of miniature dry cells which may be as small as l inch in length and 1/4 inch in diameter. It will be realized that in such tiny cells the clearance between the zinc can and bobbin of depolarizing mix is very small and it is very diilicult to avoid Contact during the various operations required to complete the cell and to avoid the depolarizing mix from becoming loosened on the carbon. In the manufacture of small cells, the ordinary closures of sealing wax are so thin that they have little strength to withstand internal pressure. In the present invention the closure is relatively strong and is well adapted to stand some rough handling, In making small cells by the conventional hand method, a loss of 20% because of defective construction is not uncommon.

In order to provide a good terminal for the carbon electrode, it is preferred to use a flanged metal cap which is embedded in the molded top closure but this cap may be omitted, if desired. The cap may be provided with a small top perforation for venting gas, or the cap may be imperforate in a leak-proof construction and an insulated steel jacket provided in accordance with my Patent No. 2,198,423 or Patent No. 2,243,938.

The invention is illustrated in a preferred embodiment in the accompanying drawings, in which- Figure 1 is a vertical sectional View showing a metal terminal cap applied to a carbon electrode; Figure 2, a sectional view of the carbon electrode and cap after the top` closure has been molded thereon; Figure 3, a sectional view showing the next step wherein depolarizing mix has been tightly packed around the carbon electrode to form a bobbin; Figure 4, -a sectional view showing the bobbin inserted in a zinc can containing electrolyte; Figure 5, a vertical sectional view of the completed cell; Figure 6, a plan sectional view, taken as indicated at line 6 of Figure 5; Figure '7, an elevational view of the completed cell; and Figure 8, a top plan view of the finished cell.

In the form illustrated, a carbon electrode 9 is provided with a metallic ilanged cap I0 which makes a pressed fit thereon. It will be understood throughout the specification and claims that the term carbon electrode is used to designate the usual centrally disposed ash light electrode and can be made of other materials than carbon, if so desired.

In the next step a top closure I I is molded onto the top of the electrode 9 and the lower ilanged portion of the cap III is embedded therein. This closure is preferably formed of a thermoplastic material such as "Tenite and may be formed in an injection press.

As shown in Figure 3, depolarizing mix I2 is tightlypacked around the lower end of the electrode and suihcient pressure is applied to make the bobbin quite hard and stand rough handling.

Another electrode I3 may be in the form of a zinc can having an inwardly struck groove I4 to form a reduced neck portion and provide shoulders I5 on which the top closure may rest. Preferably the inner top portion of the can is provided with a cementitious material I6 so that when the top is turned inwardly, as indicated at I'I in Figure 5, a very tight seal is provided. Cells formed in this manner have been found to withstand internal pressures above 200 pounds per square inch without leaking.

A suitable electrolyte I8 is placed in the can before the bobbin is introduced so that after it is introduced a small air space I9 is provided to permit some expansion of the solids as the cell is used up. The electrolyte usually contains a small amount of starch which may be jelled by immersing the can in hot water for a few moments after assembly. In some cases, it may be desired to provide additional air space between the top of the depolorizing mix and the bottom of the top closure. If additional air space is desired, it can be provided when. the bobbin is molded or a. groove may be cut in the depolarizing mix just' below the closure.

If desired, before gelatinizing the electrolyte, the cell may be inverted to provide an air space at the bottom. However, it is generally preferred to have the electrolyte in contact with the bottom of the cell so that most of the internally exposed zinc may be utilized.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom for some modifications will be obvious to those skilled in the art.

I claim:

l. The method of making a dry cell which comprises the following steps: placing a metal cap on the upper end of a carbon electrode; molding a top closure of insulating material to the upper portion of said electrode and embracing the side walls of said cap; compressing depolarizing mix 2; The method of making a dry cell which comprises the following steps: molding a top closure about the lower portion of said electrode to form 1 a bobbin; suspending said bobbin in a zinc can partially filled with electrolyte; and permanently securing said top closure in the top of said can.

of insulating material to the sides of the upper end portion of a carbon electrode; compressing depolarizing mix about the lower portion of said electrode to form a bobbin; forming a shoulder in the upper end of a zinc can; partially filling the can with electrolyte; suspending said bobbin and said can by seating the top closure in the top of the can; and permanently securing said top closure to the can.

HERMAN R. C. ANTHONY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

